A Proposed Semi-Passive Treatment System At Remote AML Sites

byRobert H. Lambeth, PE, PG, LHG & Gene Andrews, PE

Millennium Science & Engineering, Inc.Spokane, Washington

EPA HARDROCK MINING CONFERENCE 2012Denver, Colorado

April 3, 2012

Problem: ARD discharging into a popular Wild & Scenic River floodplainQuestion: Can you build a minimal cost, walk-away treatment system that has no footprint, odor, maintenance, or power needs?Answer: It would be difficult! Or more precisely – NO!

History & Description

• Volcanogenic Massive Sulfide deposit• Active 1898-1942• Most production 1908-1916• 13 Adits• 2 Shafts• 4 Levels below River• 10,000 feet of workings

Ground Level View of Site

Aerial View of Site

Y

100 Yr. Flood Plain

River Level Adit

Floodplain Looking West

All Adits

Adit Discharge

Discharge QualityFlow = 10 gpmpH = 2.9 suAl = 19 mg/LAs = 0.016 mg/LCu = 3.5 mg/LFe = 93 mg/LPb = 0.21 mg/LSe = 0.03 mg/LZn = 18 mg/L

Treatment Design Considerations• Limited access• No power• Adit frequently flooded• Entire valley is a floodplain• Visibility• Vandalism• No water availability

Basic Treatment OptionsNeutralization (mandatory)• Within wetlands?• Caustic?• Lime?

Sludge handling• Direct discharge?• Settlement basin w/removal?• Filtration w/removal

Neutralization Discussion

Lime addition• Denser sludge• Lower cost• Doesn’t freeze, but• More maintenance• Greater power requirements

Caustic addition (Preferred)• Much easier and simpler to use• Less power needs• Lower maintenance

Bench & Field Tests

• Performed by Ionic Water Technologies, Inc., Reno, NV

• 8 gpd of 30% NaOH solution to pH 9• All metals but Al declined to criteria in effluent• Sludge passed TCLP, but leachate still exceeded

some criteria• Paint filter test was not performed

This Should Work!

Settlement Option Issues

Wetlands• Would have to be in the floodplain• Will 10 gpm sustain an adequate size system for the

pH?• Visible and subject to vandalism

Settlement basins• Would have to be in the floodplain• Visible and subject to vandalism

>> Sludge removal for both awkward and the disturbed sludge may not pass the Paint Filter Test<<

Potential Locations

Y

100 Yr. Flood Plain

River Level Adit? ????

??

?? = Treatment plant? = Basins? = Pipeline

??

Alternative Proposal!

1. Concrete plug in adit• Can create head!• Stops inundation!

2. Treatment system underground• Hides it!• Protects it!

3. Treated effluent to fabric filters• Contains sludge!• Protects sludge from flooding!

4. Discharge to drainfield for polish and concealment!

Sludge Disposal ?!?• Use multiple fabric filter tubes in series!• Containerize filter tubes in large garbage

dumpsters!• Change out full filter tubes quickly!• Dispose in local landfill!• The sludge passes TCLP!• The sludge should pass the Paint Filter Test!

>>The landfill can still reject it!!<<

Flowsheet

In-Adit Design

Pipe Detail

Surface Plan View

COSTSCapital Cost = $1,900,000

Five Year Capital & Operating Cost = $2,828,000

Closing1. More treatment/pilot tests are

needed!2. This can be phased in!3. This is just one more wrench in

the ARD remedial toolbox!

Comments?

Questions?

Sticker Shock?